In a silver halide color photographic element or material a color image is formed when the element is given an imagewise exposure to light and then subjected to a color development process. In the color development process silver halide is reduced to silver as a function of exposure by a color developing agent, which is oxidized and then reacts with coupler to form dye. In most color photographic elements the coupler or couplers are coated in the element in the form of small dispersion droplets. Many photographic elements or materials contain, in addition to imaging couplers, image-modifying couplers that release a photographically useful group from the coupling site upon reaction with oxidized color developer. Couplers that release a silver development inhibitor from the coupling-off position, so-called DIR couplers, are one type of imaging modifying coupler utilized in color photographic elements.
Many photographic materials, and especially color negative films, contain DIR (development inhibitor releasing) couplers. In addition to forming imaging dye, DIR couplers release inhibitors that can restrain silver development in the layer in which release occurs as well as in other layers of a multilayer photographic material. DIR couplers can help control gamma or contrast, can enhance sharpness or acutance, can reduce granularity and can provide color correction via interlayer interimage effects. There has been a need for more effective yellow dye-forming DIR couplers. Yellow DIR couplers that provide high interimage color correction are particularly desirable for modern color negative films. In addition, it is desirable that such couplers have high activity to maximize rates and efficiencies of inhibitor release and minimize laydowns. DIR couplers that show acceptably low continued coupling when films containing them are placed in a bleach solution immediately after development (i.e. with no intervening stop bath) are also needed. It is also desirable that the inhibitors released from DIR couplers are readily hydrolyzed to weak inhibitors in the developer solution to prevent seasoning of the developer on extended use. It is further desirable that DIR couplers are thermally stable so that materials that incorporate them possess good raw stock stability. In addition, it is desirable that DIR couplers form dyes that have high extinction coefficients and good thermal stability. The DIR couplers of this invention possess all of these desirable properties, especially high activity, the propensity to provide good interlayer interimage, the release of efficient hydrolyzable inhibitors, high dye extinction coefficients and excellent dye stability.
U.S. Pat. No. 3,933,500 broadly discloses DIR couplers with azole coupling-off groups, but discloses neither the 3-indoloylacetanilide coupler parents nor the purine coupling-off groups of this invention. U.S. patent application Ser. No. 08/824,223 discloses yellow dye-forming couplers with purine coupling-off groups, but does not disclose the 3-indoloylacetanilide DIR couplers of this invention. U.S. Pat. No. 5,674,667 (EPA 751,428 A1) discloses pyrroloylacetanilide yellow dye-forming couplers with a variety of coupling-off groups. The pyrroloylacetanilide couplers of U.S. Pat. No. 5,674,667 are structurally distinct from the 3-indoloylacetanilde couplers of this invention and lack the major advantages of the couplers of this invention.